1. Field of the Invention
The present invention relates to an image pickup device and a radiation image pickup or radiographic device for picking up an object image.
2. Related Background Art
As one of radiation image pickup or radiographic devices, there is known an X-ray image pickup device that is utilized in sites of medical care and the like. There were many X-ray image pickup devices that employ a system for converting X-rays to visible light and recording the visible light on a photosensitive film in the past. In recent years, an X-ray image pickup device has been increasingly used, which employs a system for further converting an image of X-rays converted to visible light to an electric image signal, and then displaying the image by a display device.
In general, such an X-ray image pickup device is provided with: a phosphor for converting X-rays to visible light; a solid-state image pickup element as a sensor for detecting the converted visible light; and a light guiding member such as an optical fiber, which guides the converted visible light to the solid-state image pickup element.
In such a sensor, X-rays may be transmitted through the phosphor to be irradiated on the solid-state image pickup element. In this case, a noise signal generated by the incident X-rays directly entered is superimposed on an image signal by visible light. Such an image is very ugly and decreases a sense of resolution.
Thus, in order to reduce X-rays to be this noise as much as possible, measures are taken such as one for using an optical fiber containing an X-ray absorbing material such as lead.
In particular, since a compact and thin X-ray sensor such as an intraoral sensor for dental use which is used in a limited space in a mouth of a patient has a limited thickness, a thickness of the optical fiber used in the X-ray sensor is also limited. Consequently, it may not be possible to completely absorb X-rays transmitted through a phosphor to reach a solid-state image pickup element.
In order to cope with this problem, in a Japanese Patent Application Laid-open No. 6-125887, a device capable of removing an X-ray noise that is transmitted through a phosphor to reach a solid-state image pickup element is proposed. The device disclosed in Japanese Patent Application Laid-open No. 6-125887 compares data obtained from a pixel of a certain point on the solid-state image pickup element with data of neighboring pixels within a fixed range, and if a result of the comparison is equal to or more than a predetermined value, determines that the data obtained from the pixel is data containing a noise due to X-rays to correct the data by deleting and recreating it based on the data of the neighboring pixels. The processing is performed for each point on the solid-state image pickup element.
As described above, the method described in Japanese Patent Application Laid-open No. 6-125887 is for detecting and deleting data of a pixel in which a noise due to X-rays is generated and replacing the data of the pixel with correction data that is newly created based on the data of neighboring pixels.
Therefore, in some cases, deleted data could not be accurately reproduced due to the generation of an X-ray noise (hereinafter referred to as spike noise). In addition, since it was determined whether data of each pixel contains only an original signal or the original signal additionally including a spike noise using data of neighboring pixels, the processing was complicated. Further, if the data of the pixel contained a spike noise, since new data was created based on the neighboring pixels to correct the data as described above, the processing required a large arithmetic operation volume.
The present invention has been devised in view of the above-mentioned drawbacks, and it is an object of the present invention to obtain image data with few noise components.
In order to achieve the above-mentioned object, according to an embodiment of the present invention, there is provided an image pickup device characterized by comprising: a photoelectric conversion region; a driving circuit for reading out a signal generated by photoelectric conversion from an identical pixel contained in the photoelectric conversion region for a plurality of times; and a correction circuit for extracting a noise component by calculating a difference among a plurality of signals read out by the driving circuit and removing the noise component contained in the signals from the pixel using the extracted noise component.
Also, according to another embodiment of the present invention, there is provided an image pickup device characterized by comprising: a converting member for converting radiation transmitted through an object to light; a photoelectric conversion region for converting the light converted by the converting member to an electric signal; and a correction circuit for extracting a noise component generated by the radiation transmitted through the converting member to reach the photoelectric conversion region from a signal outputted by a first pixel contained in the photoelectric conversion region to remove the noise component contained in the signal from the first pixel using the extracted noise component.